I'm running PHP-based forum software on a web server. The software sends e-mail to our users when an event happens, such as sending validation e-mail, or a post was replied to, etc. I'm using IIS to host the forums, and would like to use Window's built in SMTP server to allow PHP to send mail through it.
I have it up and running and mostly working... What I did was install the SMTP server, and allowed 127.0.0.1 to relay through it so it would send e-mail out. Question One: Is this correct (and best) practice?
Question Two: The odd thing is that on about 30% of the mail servers my server connects to to send a message, I get a warning back that says, "501 Syntactically invalid HELO argument(s)" in my Event Viewer.
Technically I don't use the SMTP server to receive mail, only to send it. I assume this is because those mail servers are trying to use reverse DNS and failing because I don't have an MX record pointing to my forum server? If not, what do I do to fix that warning?